Physical health problems, including obesity, increase in the 30s, and substance use, depression, and anxiety disorders remain prevalent and often co-occur and accompany physical health problems. This study investigates the interrelationships among these problems by augmenting data from the Seattle Social Development Project (SSDP), a gender-balanced, multiethnic sample of 808 followed from age 10 through age 35. The study examines the health effects of two broad environmental domains: the social environment - defined by social interactions and developmental experiences hypothesized to affect health through positive adult functioning (in marriage, parenthood, career, community, etc.); and the built environment - defined by a neighborhood's physical features hypothesized to affect health through physical activity. The diverse sample also provides an opportunity to investigate environmental factors and mechanisms that can explain disparities in health outcomes by gender, ethnicity, and economic status. New objective measures of the built environment, physical activity, and health outcomes at age 39 are added to 14 waves of prospective data including assessments of social development throughout, and diagnostic assessments of drug abuse, mental disorders, and physical health collected every three years from age 21 through age 35. Our goal is to understand the mechanisms linking social and built environments to interrelated health problems in the 30s, including sexually transmitted infections, and the contribution of these mechanisms to explaining health disparities.